Seat belt retractor

ABSTRACT

A seatbelt retractor of the invention intends to stabilize the stopping position of a seatbelt, and to stabilize the resistance thereof. In order to absorb the energy acting on the seatbelt in case of a vehicle emergency, the seatbelt retractor includes a torsion bar 4 (first energy-absorbing means) being the rotational shaft of a take-up drum, a second energy-absorbing means utilizing the pulling of a wire, and a clutch mechanism which immediately switches a state where the first and second energy-absorbing means absorb the energy acting on the seatbelt in case of a vehicle emergency into a state where only the first energy-absorbing means absorbs the energy.

TECHNICAL FIELD

The present invention relates to a seatbelt retractor provided with anenergy-absorbing means, which, in case of a vehicle emergency, restrainsa webbing from being pulled out to restrain movements of vehicleoccupant and absorbs an impact load acting on the vehicle occupant.

BACKGROUND TECHNOLOGY

There has been known in the seatbelt retractor which imposes a largeresistive load on the seatbelt at the moment of a vehicle emergency andthereafter reduces the resistive load to achieve the security of vehicleoccupant. There has been known, as an example, JP 2001-301569A whichdiscloses a webbing take-up apparatus (seatbelt retractor) including alock base (locking base) provided on one end of a cylindrical spool(take-up drum) which winds up webbing in a manner that a relativerotation with the spool is possible, a lock means which prevents arotation of the lockbase in the direction of the webbing pulled out incase of a vehicle emergency, a torsion bar inserted into the spool, oneend of which is coupled with the spool, the other end of which iscoupled with the lock base, which generates a torsional deformation in astate where the lock means prevents a rotation of the lock base in thedirection of the webbing pulled out, a wire, one end of which is fixedto the lock base, the other end and the medium part of which areinserted into the spool, which is pulled out from the spool when thespool rotates relatively with the lock base, and a cutting means capableof cutting the wire.

In this webbing take-up apparatus, since the wire with the one endthereof fixed to the lock base is inserted into the spool (take-updrum), when a rotation of the lock base is prevented in case of avehicle emergency, the torsional load in the torsion bar and the pullingload in the wire act on the webbing as a force limiting load. And, thewire is cut at an arbitrary timing, whereby the force limiting load isreduced to only the torsional load in the torsion bar.

In the conventional webbing take-up apparatus, in the duration from themoment that the cutting means comes in contact with the wire pulled outfrom the spool (take-up drum) till the moment that the cutting meanscuts the wire away, the resistance when the pulling load restrains apull-out of the wire becomes larger than the resistance when the wire ispulled out. However, after the wire is cut away, the resistance by thewire completely disappears, and hence the difference of thetensile-force in a webbing increases in the duration. Accordingly, avehicle occupant is restrained from moving forward at the actuation ofcutting the wire, however the occupant is made to move forward abruptlyafter the wire is cut away, which creates the apprehension that theoccupant do not stop at a specified-position. Further, since the wire iscut vertically to the pull-out direction, the cutting position driftsdepending on the tensile force of the webbing, namely, the pull-outspeed of the wire being pulled out from the spool. Accordingly, thecutting is not performed at a constant position, and the resistance inthe webbing pulled out is not stabilized, which is disadvantageous.

Therefore, an object of the present invention is to solve the aboveconventional problems.

That is, the first object of the invention is to make anenergy-absorbing means which provides a resistive load capable ofappropriately selecting the amount of the energy absorption, and tothereby halt the wire at a constant position and stabilize theresistance in the webbing pulled out.

The second object is to make an energy-absorbing means which halts toprovide the load, and to make it capable of freely adjusting the timingof halting, in a manner that it is able to perform an optimum energyabsorption in correspondence with the physical make-up of vehicleoccupant, scale of a vehicle collision, and time and so forth.

The third object is to make an energy-absorbing members not generateexcessive energy absorptions in switching the resistive loads, and tostabilize the provision of load by the energy-absorbing members, so thatthe vehicle occupant can easily be halted at specified positions.

DISCLOSURE OF THE INVENTION

1. A seatbelt retractor according to a first aspect of the inventioncomprises a take-up drum on which webbing is wound, a take-up shaft, oneend of which is coupled with one end of the take-up drum in a mannerthat a relative rotation with the take-up drum is impossible, which isbiased in the direction of the webbing taken up, an emergency lockmechanism which restrains a rotation in the direction of the webbingpulled out, a clutch mechanism located near the other end of the take-upshaft, a plate body provided close to a side on the other end of thetake-up drum, which is provided on the other end of the take-up shaftthrough the clutch mechanism, and an energy-absorbing means locatedbetween the side of the take-up drum and the plate body, which providesa resistive load by mutually performing a relative rotation, wherein theclutch mechanism switches a first state where the plate body is providedon the other end of the take-up shaft in a manner that a relativerotation with the take-up shaft is impossible into a second state wherethe plate body is provided on the other end of the take-up shaft in amanner that a relative rotation with the take-up shaft is possible, andthe clutch mechanism includes a clutch release mechanism which actuatesa switching at an arbitrary timing.

2. A seatbelt retractor according to a second aspect of the inventioncomprises a take-up drum on which webbing is wound, a torsion barinserted through the take-up drum, one end of which is coupled with oneend of the take-up drum in a manner that a relative rotation with thetake-up drum is impossible, which is biased in the direction of thewebbing taken up, an emergency lock mechanism located on the other endof the torsion bar, which restrains a rotation in the direction of thewebbing pulled out, a lock actuating device which actuates the emergencylock mechanism in case of a vehicle emergency, a clutch mechanismlocated near the other end of the torsion bar, a plate body providedclose to a side on the other end of the take-up drum, which is providedon the other end of the torsion bar through the clutch mechanism, and asecond energy-absorbing means located between the side of the take-updrum and the plate body, which provides a resistive load by mutuallyperforming a relative rotation, wherein the clutch mechanism switches afirst state where the plate body is provided on the other end of thetorsion bar in a manner that a relative rotation with the torsion bar isimpossible into a second state where the plate body is provided on theother end of the torsion bar in a manner that a relative rotation withthe torsion bar is possible, and the clutch mechanism includes a clutchrelease mechanism which actuates a switching at an arbitrary timing.

In the seatbelt retractor according to the first aspect or the secondaspect of the invention, as the lock actuating device actuates theemergency lock mechanism in case of a vehicle emergency, the other endof the take-up shaft or the torsion bar is restrained from rotating inthe direction of the webbing pulled out, and the take-up drum is alsorestrained from rotating. At this moment, as the webbing is pulled outby a pull-out force more than a predetermined value, the one end of thetake-up shaft or the torsion bar 4 is coupled with the take-up drumbeing driven to rotate in a manner that a relative rotation isimpossible, and the other end thereof is coupled with the emergency lockmechanism which has restrained the rotation in a manner that a relativerotation is impossible, therefore, the take-up shaft or the torsion bar,while generating a torsional deformation, rotates the take-up drum. Atthe same time, there generates a relative rotation between the take-updrum being rotating and the plate body of which relative rotation isdisabled by the clutch mechanism on the other end of the take-up shaftor the torsion bar with the rotation restrained, and a resistive load issupplied by the second energy-absorbing (EA) means.

In the first state where a relative rotation of the plate body with theother end of the take-up shaft or the torsion bar is disabled by theclutch mechanism, the take-up shaft or the torsion bar (firstenergy-absorbing means) and the second energy-absorbing (EA) means arein operation. The clutch mechanism being put in operation through aclutch actuating mechanism at an arbitrary timing switches the platebody into the second state where the plate body is able to rotaterelatively with the other end of the take-up drum or the torsion bar,and the clutch mechanism makes the take-up shaft or the torsion baralone perform the energy absorption (EA).

Thereby, it is possible to appropriately select the amount of the energyabsorption, by actuating both of the take-up shaft or the torsion bar(first energy-absorbing means) and the second energy-absorbing means, oronly the take-up shaft or the torsion bar at the actuating time of theenergy absorption. And, after actuating the energy absorption by usingboth of the first and the second energy-absorbing means, in order toachieve an optimum energy absorption in correspondence with parameterssuch as physical make-up of vehicle occupant, scale of a vehiclecollision, and time, it is possible to stop the provision of load by thesecond energy-absorbing means on the way, and to perform the energyabsorption only by the take-up shaft or the torsion bar. Since theprovision of the resistive load is stopped without any contact with theenergy-absorbing means (wire) being the second energy-absorbing means,excessive energy absorption is not generated in the switching, theprovision of load becomes stabilized, and the vehicle occupant caneasily be halted at specified positions.

3. A seatbelt retractor according to a third aspect of the invention isthat, in the seatbelt retractor according to the second aspect of theinvention, the clutch mechanism includes in a manner that a relativerotation with the emergency lock mechanism is impossible, at least onejoint pawl pivoted to be turnable to a side of the plate body on theopposite side to the take-up drum, which comes in contact with the jointplate to turn outwardly, a release ring retained by a casing fixed on aside plate of a housing on the other end of the torsion bar to bemovable in the axial direction while rotating, which is located on aperiphery of the joint pawl; and a clutch release mechanism whichactuates the release ring attached to the casing.

According to the third aspect of the invention, when the lock actuatingdevice actuates the emergency lock mechanism, until the torsion bar andthe second energy-absorbing (EA) means provide loads in practice, thewebbing is pulled and the take-up drum is rotated in the direction ofthe webbing pulled out. At this moment, in the duration till rotatingrelatively with the take-up drum, the plate body slightly rotatesintegrally with the take-up drum, so that a relative rotation isgenerated between the plate body and the joint plate coupled with theemergency lock mechanism to be impossible of a relative rotation, andthe inner circumference of the joint pawl comes in contact with thejoint plate, which presses the joint pawl outwardly. Since-the releasering is located on a periphery of the joint pawl, the joint pawl isrestrained from expanding outwardly. As the clutch release mechanismactuates the operation, the release ring is made to move in the axialdirection of the torsion bar while rotating, and is detached from thecircumference of the joint pawl, and hence the joint pawl expandsoutwardly. Since the plate body is accordingly detached from the jointplate which has restrained the rotation of the plate body, the platebody rotates integrally with the take-up drum, the provision of theresistive load by the wire (energy-absorbing member) is halted, and onlythe energy absorption (EA) by the torsion bar is performed.

Although the plate body rotates integrally with the take-up drum in thenormal use of the seatbelt retractor, when the emergency lock mechanismactuates the operation, the plate body is put into the state where itcannot rotate integrally with the take-up drum, while when the clutchrelease mechanism of the clutch mechanism actuates the operation, it isput into the state where it can rotate integrally with the take-up drum.

Thus, according to the third aspect of the invention, if the setting ofthe clutch mechanism is performed in the assembling, the clutchmechanism can be easily installed.

Further, when the clutch release mechanism actuates the operation, theoperation is performed in the state where the clutch mechanism isrestrained from rotating, and hence the operation by the clutch releasemechanism is stabilized.

Further, at the moment when the joint pawl expands outwardly, the loadof the energy-absorbing means becomes zero without increasing, and theswitching of the load can smoothly be performed.

4. A seatbelt retractor according to a fourth aspect of the invention isthat, in the seatbelt retractor according to the third aspect of theinvention, the clutch release mechanism includes a gas generator whichgenerates gas in a cylinder attached to the casing at an arbitrarytiming, and a piston pressed and driven by a gas pressure in thecylinder, which presses the circumference of the release ring to rotatethe release ring.

Thereby, the piston pressed and driven by the gas generator in thecylinder presses the circumference of the release ring and rotates therelease ring, thus detaching the clutch.

5. A seatbelt retractor according to a fifth aspect of the invention isthat, in the seatbelt retractor according to the fourth aspect of theinvention, the release ring is provided with a contact on thecircumference thereof, which comes in contact with the piston, andplural tapered parts located with a uniform spacing on the circumferencethereof, and the casing which holds the release ring is provided withprojections corresponding to the tapered parts of the release ring.

Thereby, the tapered parts provided on the circumference of the releasering are guided to the projections of the casing, and the release ringbeing rotated is made to move in the axial direction of the torsion bar.At this moment, since the tapered parts are located on the circumferenceof the release ring with a uniform spacing, it is possible to move therelease ring in a state where the plane of the release ring is verticalto the axis.

According to the fourth and fifth aspects of the invention, although anoutward force by the joint pawl acts on the inner circumference of therelease ring, the piston driven by the gas pressure rotates the releasering in one breath, and it can release the joint pawl toward thecircumference at once in defiance of the frictional resistance bycontacts.

Since the release ring is made to move in the state where the plane ofthe release ring is vertical to the longitudinal direction of thetorsion bar, the contact of the joint pawl with the release ring isreleased at once, in the switching of the clutch, there is not anyexcessive load generated, except the load supplied by the secondenergy-absorbing means.

6. A seatbelt retractor according to a sixth aspect of the invention isthat, in the seatbelt retractor according to any one of the firstthrough the fifth aspects of the invention, the clutch mechanism isprovided with a pawl holder which positions and supports the jointpawls, and the pawl holder is provided with ribs integrally formedthereon, which biases the joint pawls in the axial direction and willnot return the joint pawls to the initial positions after operating thejoint pawls.

Thereby, the positions of the joint pawls in the first state aremaintained by biasing the springs. The outwardly expanded joint pawlsare restrained from returning to the initial positions by the ribs ofthe pawl holder, and are retained at the positions where they areexpanded. Further, the joint pawls retained there restrain the releasering from returning to the circumference of the joint pawls.

7. A seatbelt retractor according to a seventh aspect of the inventionis that, in the seatbelt retractor according to any one of the secondthrough the sixth aspects of the invention, the second energy-absorbingmeans includes a curved path provided on a side of the take-up drum onthe other end of the torsion bar, and a wire, one end of which is fixedto a take-up part of the plate body, a substantially medium part ofwhich is located in the curved groove.

Thereby, when the emergency lock mechanism actuates the operation, atensile force acting on the webbing which exceeds a predetermined valuegenerates a relative rotation between the take-up drum being rotatingand the plate body on the other end of the torsion bar with the rotationrestrained, and hence the take-up drum being rotating winds up the wire,one end of which is fixed to the take-up part of the plate body with therotation restrained, into the take-up part of the plate body, whiledeforming the wire in the curved path at any time.

According to the sixth and seventh aspects of the invention, since thejoint pawls are biased by a spring force, if, in the normal use of theseatbelt retractor, the joint pawls are made to rotate together with thetake-up drum and so forth, the joint pawls will be positioned at thespecified positions, which stabilizes the operation of the joint pawls.

The plate body prevents the joint pawls and the release ring fromreturning to specified positions in the first state where the plate bodyis provided on the other end of the take-up drum in a manner that arelative rotation is impossible from the second state where the platebody is provided on the other end of the take-up drum in a manner that arelative rotation is possible. Therefore, it is possible to stabilize aresistive load by the torsion bar without adding a load by the secondenergy-absorbing means.

It is also possible to make the second energy-absorbing means at lowcost with a simple structure, without using a member separately.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of the whole seatbelt retractor according to thepresent invention;

FIG. 2 is an exploded perspective view explaining the assembling of ahousing, a take-up drum, a torsion bar, a locking base, a base stopper,and so forth of the seatbelt retractor illustrated in FIG. 1;

FIG. 3 is an exploded perspective view explaining the assembling of thetake-up drum, the plate assembly, a retainer, and a pawl holder;

FIG. 4 is an exploded perspective view explaining the assembling of aplate assembly which is illustrated in FIG. 3;

FIG. 5 is a side view of the plate assembly;

FIG. 6 is a front view partly in section of the plate assembly;

FIG. 7 is a partly enlarged front view in section illustrating anotherembodiment of the plate assembly;

FIG. 8 is a front view in section of an assembly in which the plateassembly and the take-up drum illustrated in FIG. 3 are assembled;

FIG. 9 is a partly cutaway side view of the assembly illustrated in FIG.8;

FIG. 10 is a front view in section, in which the assembly illustrated inFIG. 8 is turned;

FIG. 11 is a partly cutaway side view of the assembly illustrated inFIG. 10;

FIG. 12 is an exploded perspective view explaining the assembling of ahousing, a casing, and so forth, which are illustrated in FIG. 2;

FIG. 13 is an exploded perspective view of a release ring, the casing, apiston, a gas generator, a gas generator holder, and so forth;

FIG. 14 is an enlarged perspective view of the pawl holder;

FIG. 15 is an enlarged perspective view of a joint pawl;

FIG. 16 is a partly cutaway side view of a clutch mechanism beforeactuating the operation;

FIG. 17 is a plan view in section of the clutch mechanism illustrated inFIG. 16;

FIG. 18 is a partly cutaway side view explaining a state where theclutch mechanism is engaged (first state);

FIG. 19 is a plan view in section of the clutch mechanism illustrated inFIG. 18;

FIG. 20 is a partly cutaway side view explaining a state where theclutch mechanism is released (second state);

FIG. 21 is a plan view in section of the clutch mechanism illustrated inFIG. 20;

FIG. 22 is an exploded perspective view explaining the assembling of thelocking base, a lock clutch, a cover, and so forth;

FIG. 23 is an exploded perspective view explaining the assembling of thetorsion bar, the lock pawl, the locking base, and so forth; and

FIG. 24 is a diagram illustrating the relation between a tensile forceacting on the webbing and the amount of the webbing pulled out.

BEST MODE FOR CARRYING OUT THE INVENTION

The preferred embodiment of the seatbelt retractor according to thepresent invention will be described in detail with reference to theaccompanying drawings.

FIG. 1 is a front view of the whole seatbelt retractor according to theinvention, and FIG. 2 is an exploded perspective view explaining theassembling of a take-up drum 2, a connector 3, a housing 9, a torsionbar 4, a locking base 5, a base stopper 7, and so forth which constitutethe major part of the seatbelt retractor illustrated in FIG. 1.

In FIG. 2, the seatbelt retractor is provided with the substantiallycylindrical take-up drum 2 on which webbing is wound. The torsion bar 4is inserted through the center of the take-up drum 2, and one end of thetorsion bar 4 is coupled integrally with one end of the take-up drum 2by means of the connector 3, described later, and it is supported by apair of side plates (9 b, 9 c) to freely rotate. A spiral spring 19(FIG. 1) is mounted on the side plate 9 c, which constantly biases thetake-up drum 2 to rotate in the take-up direction of the webbing, andthe torsion bar 4 is biased to rotate in the take-up direction of thewebbing.

Here, the seatbelt retractor in this embodiment has the structure whichwinds up slackness in the webbing by a gas pressure, and so forth incase of a vehicle emergency such as a collision, and restrains themovements of vehicle occupant by a pretensioner 15 (FIG. 1) furnished onthe side plate 9 c.

The locking base 5 resembling a substantially disk-like shape is coupledintegrally with the other end outside of the torsion bar 4 on the sideof the side plate 9 b of the housing, and it constitutes an emergencylock mechanism which restrains a rotation in the direction of thewebbing pulled out.

A clutch mechanism, described later, is located near the other end ofthe torsion bar 4, while a second energy-absorbing means, describedlater, is located on the other end of the torsion bar 4, close to theside on the other end of the take-up drum 2, wherein the torsion bar 4(first energy-absorbing means) and the second energy-absorbing meansperform the absorption of impact energy in case of a vehicle emergency.

The housing 9 is made from a metal plate by a press-molding in a mannerthe right and left side plates (9 b, 9 c) rise up from both the sides ofa back-plate fixed to the vehicle body, and the section of the housingforms a substantially U-letter.

The base stopper 7 is to prevent the locking base 5 from coming off fromthe take-up drum 2.

First Energy-Absorbing Means

Next, the first energy-absorbing means will be described.

As shown in FIG. 2, the one end of the torsion bar 4 is engaged with ahole of the connector 3 having the same shape thereof, and the other endis coupled with the locking base 5 to be able to rotate integrally.

The connector 3 is supported to freely rotate with the opening 9 d boredon the side plate 9 c of the housing 9, and it is also engaged with ahexagonal engagement recess being formed on the one end of the take-updrum 2 to correspond with the external shape of the connector 3, wherebythe torsion bar 4 is capable of rotating integrally with the take-updrum 2.

Therefore, even if the emergency lock mechanism actuates the operationand the other end of the torsion bar 4 is fixed, the one end of thetorsion bar 4 will rotate integrally with the take-up drum 2 by thewebbing being pulled out. That is, the torsion bar 4 is twisted by therotational force of the take-up drum 2, thus the energy of pulling outthe webbing can be absorbed by the torsion resistance thereof.

In this manner, the torsion bar 4 functions as the firstenergy-absorbing means.

Second Energy-Absorbing Means

Next, the second energy-absorbing means will be described with referenceto FIG. 3 through FIG. 6.

FIG. 3 is an exploded perspective view explaining the assembling of aplate assembly 2 e. The plate assembly 2 e comprises a plate body 2 a, aspiral wire 2 b with plural winds, and a disk member 2 c having pluralprojections 2 q located circumferentially around a center hole.

In FIG. 3, one end 2 g of the wire is fixed to the plate body 2 a, andthe other end 2 h of the wire is suspended to the backside of the diskmember 2 c (viewed from FIG. 3).

FIG. 4 is an exploded perspective view illustrating the whole of thesecond energy-absorbing means. The plate assembly 2 e and the take-updrum 2 are attached with a retainer 2 d.

FIG. 5 is a side view of the plate assembly 2 e, and FIG. 6 is a frontview partly in section of the same, wherein the plate assembly 2 e isassembled with the plate body 2 a, the wire 2 b, and the disk member 2c, as illustrated in FIG. 3.

In FIG. 4, a substantially circular receiving recess 2 f whichconstitutes a part of the second energy-absorbing means is formed on theside where the locking base is mounted on the take-up drum 2, namely, onthe end face of the left side in the drawing. Further, an engagementhole 2 k which receives a boss 5 c (FIG. 2) of the locking base isformed on the center of the receiving recess 2 f. The engagement pins 14to be engaged with the wire 2 b are formed at specified places on theperiphery of the receiving recess 2 f positioned outside the engagementhole 2 k on the bottom face. And, the slopes 2 t (FIG. 5) are formed atthe specified places for engaging with the wire 2 b. In this case, threesemi-circular engagement pins 14 are formed integrally to project fromthe bottom face of the receiving recess 2 f along the circumferencethereof, wherein the wire 2 b is formed in spiral, and the circumference2 i thereof (FIG. 3) is formed in curvature, which conforms to thecircular sliding face of the engagement pins 14.

FIG. 5 is a side view of the plate assembly 2 e in which the individualcomponents illustrated in FIG. 3 are assembled. As illustrated in thedrawing, the disk member 2 c and the plate body 2 a are engagedintegrally with each other in a state where the spiral wire 2 b isinterposed between both. That is, the plate body 2 a and the disk member2 c form a take-up part 2 m with a distance approximately equivalent tothe diameter of the wire 2 b, and the disk member 2 c is coupled withthe plate body 2 a in a manner that a relative rotation between both isimpossible. At this moment, the curved one end 2 g of the wire 2 b isplaced and fixed in a curved groove 2 n (FIG. 6) of the plate body 2 a.

Thus, the wire 2 b having the one end thereof fixed to the plate body 2a passes through the gap between the plate body 2 a and the disk member2 c, and when the take-up drum 2 and the plate assembly 2 e perform arelative rotation, the wire 2 b reaches the upper face of the plate body2 a being the take-up part 2 m.

The disk member 2 c covers take-up part 2 m of the plate body 2 a andthe one end 2 g of the wire 2 b in the assembly state.

FIG. 6 is a front view which shows the internal structure of the plateassembly 2 e, part of which is sectioned. As illustrated in the drawing,the curved groove 2 n is formed on the take-up part 2 m of the platebody 2 a by means of substantially semi-circular plural projections 2 p,and the one end 2 g of the wire 2 b is placed in the curved groove 2 nand is coupled therewith. The curvature radius of the curved groove 2 nis formed smaller than that of the curved path 2 j (FIG. 4) of thetake-up drum 2.

FIG. 7 illustrates another embodiment of the curved groove 2 n. In theplural projections 2 p of the plate body 2 a, at least one set of ribs 2r facing to each other are formed between the projections 2 p formingthe curved groove 2 n, and the gap between the ribs 2 r is made narrowerthan the diameter of the wire 2 b.

FIG. 8 is a front view in section illustrating a state where the take-updrum 2 illustrated in FIG. 4 and the plate assembly 2 e are assembled,and FIG. 9 is a partly cutaway side view of the assembly illustrated inFIG. 8. FIG. 10 is a front view in section, illustrating a state wherethe take-up drum 2 rotates to a certain degree after the emergency lockmechanism actuates the operation in the assembly illustrated in FIG. 8,and FIG. 11 is a partly cutaway side view in the same state.

The second energy-absorbing means having the above construction iscontained in a space delimited between the take-up drum 2 and thelocking base 5. After the emergency lock mechanism actuates theoperation, as the take-up drum 2 rotates, the wire 2 b illustrated inFIG. 8 and FIG. 9 is wound into the take-up part 2 m, as illustrated inFIG. 10 and FIG. 11.

At this moment, the wire 2 b relatively moves between the disk member 2c and the plate body 2 a, along the curved circumference 2 i projectedfrom the circumferential face of the disk member 2 c, while sliding onthe three semi-circular engagement pins 14 of the take-up drum 2.

When the emergency lock mechanism actuates the operation, in case of avehicle emergency such as a collision, the locking base 5 coupled withthe other end of the torsion bar 4 is blocked in rotating in thedirection of the webbing pulled out. And, when a rotational torque morethan a predetermined value acts on the take-up drum 2, due to the loadacting on the webbing, the one end of the torsion bar 4 (firstenergy-absorbing means) actuates a torsional deformation.

Thereby, the take-up drum 2 rotates to a degree corresponding to thetorsional deformation in the torsion bar 4, and at the same time, theother end of the torsion bar 4, which is fixed, rotates in the directionof the webbing pulled out, whereby the impact energy is absorbed. And,the actuation of the torsional deformation in the torsion bar 4generates a relative rotation between the take-up drum 2 and the lockingbase 5. The absorption of the impact energy by the secondenergy-absorbing means actuates based on this relative rotation.

While the take-up drum 2 rotates relative to the locking base 5, theplate body 2 a to which the one end 2 g of the wire 2 b is fixed iscoupled with the locking base 5, and it does not rotate, while since theengagement pins 14 formed integrally with the take-up drum 2 turn, thewire 2 b is pulled between the engagement pins 14. That is, the wire 2 bslides between the engagement pins 14 while being positioned by theslopes 2 t, while being sequentially pulled to meander between theengagement pins 14. At this moment, there generate a high slidingresistance and a bending resistance in the wire 2 b, and hence thesliding resistance and the bending resistance absorb the impact energy.

That is, when the emergency lock mechanism actuates the operation incase of a vehicle emergency, and the load acting on the take-up drum 2in the direction of the webbing pulled out is increased more than apredetermined value, both the torsion bar 4 (first energy-absorbingmeans) and the second energy-absorbing means operate as theenergy-absorbing mechanism, and absorb the impact energy in case of avehicle emergency.

Clutch Mechanism

Next, the clutch mechanism will be described which releases theengagement of the plate body 2 a with the locking base 5 of theemergency lock mechanism, and puts the plate body 2 a from the state ofa relative rotation with the take-up drum 2 being possible into thestate of a united rotation with the take-up drum 2 being possible withthe locking base 5 detached.

This clutch mechanism switches the first state where a relative rotationof the plate body 2 a with the other end of the torsion bar 4 isimpossible into the second state where a relative rotation of the platebody 2 a with the other end of the torsion bar 4 is possible. It alsocomprises the clutch release mechanism which actuates the switching atan arbitrary timing after detecting a vehicle collision.

The clutch mechanism comprises, as shown in FIG. 2, a joint plate 5 b(FIG. 23) coupled with the emergency lock mechanism in a manner that arelative rotation is impossible, and three joint pawls 12 being pivotedto be turnable on the opposite side of the take-up drum 2 to the platebody 2 a, which are in face contact with the joint plate 5 b to turnoutward.

The joint pawl 12 (FIG. 15) is a bow-formed member, and a pin 12 b isformed on the one end thereof. The pin 12 b is pivoted on the oppositeside of the take-up drum 2 to the plate body 2 a. The joint pawl 12turns with the pin 12 b as the center. Further, the joint pawl 12 has aninner projection 12 a (FIG. 15) formed on the center of the inner wall,and a notch 12 c (FIG. 15) formed on the other end inside.

A pawl holder 13 (resin spring) (FIG. 14) in a sectional concave andcircular form is provided in order to position and support the jointpawls 12. The pawl holder 13 is provided, on the circumference thereofin correspondence with the positions of the joint pawls 12, withnail-formed parts 13 c each having ribs 13 a formed thereon. Inwardlyslant slopes 13 b formed on the ribs 13 a and the nail-formed parts 13 ccome into contact with the outer faces of the joint pawls 12. Thiscontact and the resin spring functions to bias the joint pawls 12continuously toward the axial center.

Meanwhile, as the joint pawls 12 turn outward against the elasticity ofthe resin spring and climb over the ribs 13 a of the pawl holder 13, thepawl holder 13 is released from being pressed, the nail-formed parts 13c return to the insides of the joint pawls 12, and rib backsides 13 d ofthe pawl holder 13 come into contact with notches 12 c of the jointpawls 12. On the other hand, since the plate body 2 a is provided withprojections 2 s which restrain the joint pawls 12 from turning relativeto the plate body 2 a immediately after the joint pawls 12 climb overthe ribs 13 a of the pawl holder 13, the joint pawls 12 are clamped bythe rib backsides 13 d of the pawl holder and the projections 2 s of theplate body so that the joint pawls 12 are prevented from turning to theplate body 2 a.

Therefore, after the clutch is detached once, the clutch will notoperate again.

Clutch Release Mechanism

FIG. 12 is an exploded perspective view explaining the assembling of arelease ring 8, the housing 9, a casing 10, and so forth being thecomponents for releasing the clutch. FIG. 14 is an enlarged explodedperspective view of the release ring 8, the casing 10, a piston 10 a, agas generator 10 b, a gas generator holder 11, and so forth, which areillustrated in FIG. 13.

The clutch release mechanism will be described with reference to FIG. 12and FIG. 13. The release ring 8 is mounted to be rotatable on the casing10 fixed to the side plate 9 b of the housing on the other side of thetorsion bar 4 (FIG. 2), which is located on the circumferences of thejoint pawls 12.

As illustrated in FIG. 12 and FIG. 13, the clutch release mechanism ismade up with the casing 10, the gas generator 10 b which generates gasin a cylinder 10 e at an arbitrary timing after detecting a vehiclecollision, and the piston 10 a, which is pressed and driven by the gaspressure in the cylinder, and presses the circumference of the releasering 8 to rotate the release ring 8. The gas generator 10 b is attachedto the casing 10 by the gas generator holder 11.

The release ring 8 is provided with a contact 8 b which comes in contactwith the piston 10 a, and three tapered parts 8 a located with a uniformspacing on the circumference thereof. On the other hand, the casing 10which holds the release ring 8 is provided with tapered projections 10 dcorresponding to the tapered parts 8 a of the release ring 8 rotated.

In the operation, the piston 10 a pressed and driven by the gas pressurecomes in contact with the contact 8 b formed on the circumference of therelease ring 8, and hence the release ring 8 rotates. Thereby, thetapered parts 8 a of the release ring 8 are guided by the taperedprojections 10 d of the casing, and the release ring 8 retreats towardthe take-up drum 2 (FIG. 2) and retreats from the circumferences of thejoint pawls 12 (FIG. 2).

Next, the operation of the clutch mechanism will be described based onFIG. 16 through FIG. 21.

FIG. 16 through FIG. 21 are partly cutaway side views and plan views insection, which explain the operation of the clutch mechanism.

In FIG. 16 through FIG. 21, as already described, the clutch mechanismswitches the first state where a relative rotation of the plate body 2 awith the other end of the torsion bar 4 is impossible into the secondstate where a relative rotation of the plate body 2 a with the other endof the torsion bar 4 is possible.

In the assembly state, the joint pawls 12 are biased toward the axialcenter by the slopes 13 b (FIG. 14) formed on the ribs 13 a of the pawlholder 13. The three joint pawls 12 are fixed at the most inwardlyconvergent position, in non-contact with the inner circumference of therelease ring 8, and the inner projections 12 a of the joint pawls 12 arein contact with projections 5 d of the joint plate 5 b.

Here, as the emergency lock mechanism actuates the operation, anengagement tooth 6 b of a lock pawl 6 (FIG. 23) engages with the lockteeth 9 a (FIG. 2) formed on the side plate 9 b of the housing, thusgenerating a relative rotation between the joint plate 5 b and the platebody 2 a which will continue to rotate. At this moment, a relativerotation is generated between the joint pawls 12 and the projections 5 dof the joint plate, whereby the projections 5 d of the joint plate pressthe inner projections 12 a of the joint pawls 12, so that the jointpawls 12 receive a force toward the circumference, and they are prone toexpand outwardly.

When the force exceeds the biasing force of the pawl holder 13, thejoint pawls 12 come in contact with the inner-circumferential wall ofthe release ring 8. When the joint pawls 12 come in contact with theinner-circumferential wall of the release ring 8 and the outwardexpansion thereof is restrained, the locking base 5 and the plate body 2a become integrated with each other, and a relative rotation isgenerated between the take-up drum 2 and the plate body 2 a, so that thewire 2 b is pulled and the second energy absorption is performed, inaddition to the energy absorption by the torsion bar 4.

Next, as the clutch release mechanism actuates the operation in thisstate, the piston 10 a (FIG. 13) operates to rotate the release ring 8,whereby the rotation of the release ring 8 guides the tapered parts 8 aof the release ring 8 to the tapered projections 10 d of the casing(FIG. 13). Thus, the release ring 8 retreats toward the take-up drum 2,and retreats from the circumferences of the joint pawls 12 at the sametime. The joint pawls 12 come in face contact with the joint plate 5 bto expand outwardly, and become detached from the projections 5 d of thejoint plate, whereby the plate body 2 a is released from the lockingbase 5.

That is, as the clutch mechanism actuates the operation to move therelease ring 8 in the axial direction, as illustrated in FIG. 20 andFIG. 21, the joint pawls 12 expand outward, and the projections 5 d ofthe joint plate are completely detached from the joint pawls 12, andhence the locked state where the locking base 5 and the plate body 2 aare integrally fixed is released. In consequence, the pull-out motion ofthe wire 2 b is halted, and the plate body 2 a and the take-up drum 2become rotatable integrally. However, since the take-up drum 2 and thelocking base 5 continue a relative rotation even in this case, thetorsion bar 4 alone continues the energy absorption.

Emergency Lock Mechanism

FIG. 22 is an exploded perspective view explaining the assembling of theemergency lock mechanism, which is made up with the locking base 5, alock clutch 16, a cover 18, and so forth. FIG. 23 is an explodedperspective view explaining the assembling of the torsion bar 4, thelock pawl 6, the locking base 5, and so forth.

As a concrete construction of the emergency lock mechanism, variousknown ones may be adopted. As one example, as illustrated in FIG. 22 andFIG. 23, a spring receiving part 16 a is formed to project on one sideof the lock clutch 16, and the spring receiving part 16 a is engaged tobe relatively movable with a play inside a spring containing part 5 aresembling a recessed-groove shape, which is formed on the locking base5.

At this moment, the spring receiving part 16 a is elastically biased ina specified direction by a return spring 17 made of a coil springretained in the spring containing part 5 a, and the lock clutch 16 ismade to rotate synchronously with the locking base 5 in a state of beingbiased in the direction of the webbing pulled out.

The torsion bar 4 is inserted in a hole bored through the cylindricalboss 5 c, which is formed to project from the side of the locking base 5in the direction of facing the take-up drum 2, whereby, the torsion bar4 is coupled with the locking base 5 to be rotatable integrally.

The lock clutch 16 has a projected guide groove 16 c formed thereon, andinto the guide groove 16 c, an interlocking pin 6 a formed on the lockpawl 6 (FIG. 23) is slid and guided. The interlocking pin 6 a is made tobe slid and guided into the projected guide groove 16 c by a relativerotation of the lock clutch 16 and the locking base 5 against thebiasing force by the return spring 17. This sliding and guiding of theinterlocking pin 6 a makes it possible to freely project or retreat theengagement tooth 6 b of the lock pawl 6 from the circumference of thelocking base 5.

The emergency lock mechanism is made up with the locking base 5, thelock pawl 6, the lock teeth 9 a (FIG. 2) formed on the housing 9, thelock clutch 16, and so forth.

In order to actuate the emergency lock mechanism, a cover 18 is providedwith a lock actuating mechanism which actuates the emergency lockmechanism in response to an abrupt pull-out of the webbing and an abruptvariation in the acceleration.

The locking base 5 and the lock pawl 6 are attached with the joint plate5 b.

The engagement tooth 6 b is formed on a tip of the lock pawl 6, and thelock pawl 6 is located to be slidable on the locking base 5 by theinterlocking pin 6 a. The lock teeth 9 a with which the engagement tooth6 b of the lock pawl 6 is able to engage are formed on the side plate 9b of the housing 9, and in case of a vehicle emergency, the engagementtooth 6 b of the lock pawl 6 is engaged with the lock teeth 9 a, andthis engagement restrains the locking base 5 from rotating in thedirection of the webbing pulled out.

According to the invention thus described, since the secondenergy-absorbing means is contained in a space delimited by the take-updrum 2 and the locking base 5, there is not a substantial size expansionin the axial direction of the seatbelt retractor to sacrifice thecompactification, although the second energy-absorbing means is providedseparately from the torsion bar 4. Further, the structures of the wire 2b and the engagement pins 14 which constitute the secondenergy-absorbing means are equally simple, and the manufacturing processthereof is rather simple as well.

FIG. 24 is a diagram illustrating the relation between a tensile forceacting on the webbing and the amount of the webbing pulled out.

The whole energy-absorbing load of the seatbelt retractor is the sum f3of an energy-absorbing load f1 when the torsion bar 4 generates atorsional deformation and an energy-absorbing load f2 by the secondenergy-absorbing means, as illustrated in FIG. 24.

In case of a high energy-absorbing load, the relation between both formsa curve O, A, B, D, F in case of a low energy-absorbing load, it forms acurve O, A, C, E by the switching by the clutch mechanism, and, in caseof a medium energy-absorbing load, it forms a curve O, A, B, D, C, E.

Further, with regard to the area of the energy absorption by thetorsional deformation in the torsion bar 4, the area of the energyabsorption by the sliding resistance of the second energy-absorbingmeans can be set freely independently.

For example, the area of the energy absorption by the secondenergy-absorbing means can be set to overlap a part of the area of theenergy absorption by the torsional deformation in the torsion bar 4,thereby securing a high energy-absorbing load equivalent to the sum ofboth the energy-absorbing loads, in the part of the area of the energyabsorption by the torsional deformation in the torsion bar 4. In thearea where both the energy-absorbing areas do not overlap each other, alow energy-absorbing load can be set only by the energy-absorbingfunction by the torsional deformation in the torsion bar 4. Thus, it ispossible to provide the energy-absorbing mechanism of the seatbeltretractor with such an energy-absorbing characteristic in which theenergy-absorbing load varies during the operation.

Further, the adjustment of the whole energy-absorbing load of theseatbelt retractor is related to various factors such that it is relatednot only to the modifications of the diameter and material of thetorsion bar 4, but also to the modifications of the size, shape, andmaterial of the second energy-absorbing means. For example, it ispossible to realize a desired energy-absorbing load, not depending onthe modifications such as expansion of the diameter of the torsion bar 4and modification of the material thereof, but by means of the designmodification of the other remaining factors. That is, it is possible toeasily set the energy-absorbing load high, without sacrificing thecompactification of the seatbelt retractor by reducing the diameters ofthe torsion bar 4 and the take-up drum 2. And, in case that the size andthe material of both the torsion bar 4 and the second energy-absorbingmeans can be modified, by adjusting the energy-absorbing load andadjusting the energy-absorbing area in both the means, it becomespossible to easily meet the demand for a specific energy characteristicbased on differences of the vehicle structure, and also possible toflexibly meet various needs.

Meanwhile, it is preferable to set the adjustment of the slidingresistance between the wire 2 b and the engagement pins 14 based onvarious factors such as a shape of the curved path, roughness of thecontact faces of both, and size of the contact area and so forth. Whenthe adjustment of the sliding resistance is set based on various factorsin this manner, for example, if a modification of part of the factorsbecomes difficult due to the restrictions of the dimensions, modifyingthe other factors will make it possible to adjust the sliding resistancecomparably easily to an arbitrary value required.

The seatbelt retractor of the invention is provided with the torsion bar4 and the second energy-absorbing means, and also employs the clutchmechanism. Thereby, it is possible to appropriately select the amount ofthe energy absorption, by actuating both or only the torsion bar 4 atthe actuating time of the energy absorption. And, after actuating theenergy absorption by using both, in order to achieve an optimum energyabsorption in correspondence with parameters such as physical make-up ofvehicle occupant, scale of a vehicle collision, and time, it is possibleto stop the provision of load by the second energy-absorbing means onthe way, and to perform the energy absorption only by the torsion bar.

INDUSTRIAL APPLICABILITY

The present invention is useful for a seatbelt retractor which absorbsan impact load acting on a vehicle occupant in case of a vehicleemergency such as a collision, and secures the vehicle occupant.

1. A seatbelt retractor comprises: a take-up drum on which webbing iswound; a take-up shaft, one end of which is coupled with one end of thetake-up drum in a manner that a relative rotation with the take-up drumis impossible, which is biased in the direction of the webbing taken up;an emergency lock mechanism which restrains a rotation in the directionof the webbing pulled out; a clutch mechanism located near the other endof the take-up shaft; a plate body provided close to a side on the otherend of the take-up drum, which is provided on the other end of thetake-up shaft through the clutch mechanism; and an energy-absorbingmeans located between the side of the take-up drum and the plate body,which provides a resistive load by mutually performing a relativerotation; wherein the clutch mechanism switches a first state where theplate body is provided on the other end of the take-up shaft in a mannerthat a relative rotation with the take-up shaft is impossible into asecond state where the plate body is provided on the other end of thetake-up shaft in a manner that a relative rotation with the take-upshaft is possible, and the clutch mechanism includes a clutch releasemechanism which actuates a switching at an arbitrary timing.
 2. Aseatbelt retractor comprising: a take-up drum on which webbing is wound;a torsion bar inserted through the take-up drum, one end of which iscoupled with one end of the take-up drum in a manner that a relativerotation with the take-up drum is impossible, which is biased in thedirection of the webbing taken up; an emergency lock mechanism locatedon the other end of the torsion bar, which restrains a rotation in thedirection of the webbing pulled out; a lock actuating device whichactuates the emergency lock mechanism in case of a vehicle emergency; aclutch mechanism located near the other end of the torsion bar; a platebody provided close to a side on the other end of the take-up drum,which is provided on the other end of the torsion bar through the clutchmechanism; and a second energy-absorbing means located between the sideof the take-up drum and the plate body, which provides a resistive loadby mutually performing a relative rotation; wherein the clutch mechanismswitches a first state where the plate body is provided on the other endof the torsion bar in a manner that a relative rotation with the torsionbar is impossible into a second state where the plate body is providedon the other end of the torsion bar in a manner that a relative rotationwith the torsion bar is possible, and the clutch mechanism includes aclutch release mechanism which actuates a switching at an arbitrarytiming.
 3. A seatbelt retractor according to claim 2, wherein the clutchmechanism includes: a joint plate coupled with the emergency lockmechanism in a manner that a relative rotation with the emergency lockmechanism is impossible; at least one joint pawl pivoted to be turnableto a side of the plate body on the opposite side to the take-up drum,which comes in contact with the joint plate to turn outwardly; a releasering retained by a casing fixed on a side plate of a housing on theother end of the torsion bar to be movable in the axial direction whilerotating, which is located on a periphery of the joint pawl; and aclutch release mechanism which actuates the release ring attached to thecasing.
 4. A seatbelt retractor according to claim 3, wherein the clutchrelease mechanism includes a gas generator which generates gas in acylinder attached to the casing at an arbitrary timing, and a pistonpressed and driven by a gas pressure in the cylinder, which presses thecircumference of the release ring to rotate the release ring.
 5. Aseatbelt retractor according to claim 4, wherein the release ring isprovided with a contact on the circumference thereof, which comes incontact with the piston, and plural tapered parts located with a uniformspacing on the circumference thereof, and the casing which holds therelease ring is provided with projections corresponding to the taperedparts of the release ring.
 6. A seatbelt retractor according to claim 1,wherein the clutch mechanism is provided with a pawl holder whichpositions and supports the joint pawls, and the pawl holder is providedwith ribs integrally formed thereon, which biases the joint pawls in theaxial direction and will not return the joint pawls to the initialpositions after operating the joint pawls.
 7. A seatbelt retractoraccording to claim 2, wherein the second energy-absorbing means includesa curved path provided on a side of the take-up drum on the other end ofthe torsion bar, and a wire, one end of which is fixed to a take-up partof the plate body, a substantially medium part of which is located inthe curved groove.